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YEAR 3<br />

PROBLEM-SOLVING<br />

IN MATHEMATICS<br />

<strong>Number</strong> <strong>and</strong> place value – 2<br />

Two-time winner of the Australian<br />

Primary Publisher of the <strong>Year</strong> Award


<strong>Problem</strong>-<strong>solving</strong> in mathematics<br />

(Book D)<br />

Published by R.I.C. Publications ® 2008<br />

Copyright © George Booker <strong>and</strong><br />

Denise Bond 2007<br />

RIC–<strong>20731</strong><br />

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original purchaser for use with their class(es). The<br />

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PO Box 332 Greenwood Western Australia 6924<br />

Website: www.ricpublications.com.au<br />

Email: mail@ricgroup.com.au


FOREWORD<br />

Books A–G of <strong>Problem</strong>-<strong>solving</strong> in mathematics have been developed to provide a rich resource for teachers<br />

of students from the early years to the end of middle school <strong>and</strong> into secondary school. The series of problems,<br />

discussions of ways to underst<strong>and</strong> what is being asked <strong>and</strong> means of obtaining solutions have been built up to<br />

improve the problem-<strong>solving</strong> performance <strong>and</strong> persistence of all students. It is a fundamental belief of the authors<br />

that it is critical that students <strong>and</strong> teachers engage with a few complex problems over an extended period rather than<br />

spend a short time on many straightforward ‘problems’ or exercises. In particular, it is essential to allow students<br />

time to review <strong>and</strong> discuss what is required in the problem-<strong>solving</strong> process before moving to another <strong>and</strong> different<br />

problem. This book includes extensive ideas for extending problems <strong>and</strong> solution strategies to assist teachers in<br />

implementing this vital aspect of mathematics in their classrooms. Also, the problems have been constructed <strong>and</strong><br />

selected over many years’ experience with students at all levels of mathematical talent <strong>and</strong> persistence, as well as<br />

in discussions with teachers in classrooms, professional learning <strong>and</strong> university settings.<br />

<strong>Problem</strong>-<strong>solving</strong> does not come easily to most people,<br />

so learners need many experiences engaging with<br />

problems if they are to develop this crucial ability. As<br />

they grapple with problem, meaning <strong>and</strong> find solutions,<br />

students will learn a great deal about mathematics<br />

<strong>and</strong> mathematical reasoning; for instance, how to<br />

organise information to uncover meanings <strong>and</strong> allow<br />

connections among the various facets of a problem<br />

to become more apparent, leading to a focus on<br />

organising what needs to be done rather than simply<br />

looking to apply one or more strategies. In turn, this<br />

extended thinking will help students make informed<br />

choices about events that impact on their lives <strong>and</strong> to<br />

interpret <strong>and</strong> respond to the decisions made by others<br />

at school, in everyday life <strong>and</strong> in further study.<br />

Student <strong>and</strong> teacher pages<br />

The student pages present problems chosen with a<br />

particular problem-<strong>solving</strong> focus <strong>and</strong> draw on a range<br />

of mathematical underst<strong>and</strong>ings <strong>and</strong> processes.<br />

For each set of related problems, teacher notes <strong>and</strong><br />

discussion are provided, as well as indications of<br />

how particular problems can be examined <strong>and</strong> solved.<br />

Answers to the more straightforward problems <strong>and</strong><br />

detailed solutions to the more complex problems<br />

ensure appropriate explanations, the use of the<br />

pages, foster discussion among students <strong>and</strong> suggest<br />

ways in which problems can be extended. Related<br />

problems occur on one or more pages that extend the<br />

problem’s ideas, the solution processes <strong>and</strong> students’<br />

underst<strong>and</strong>ing of the range of ways to come to terms<br />

with what problems are asking.<br />

At the top of each teacher page, there is a statement<br />

that highlights the particular thinking that the<br />

problems will dem<strong>and</strong>, together with an indication<br />

of the mathematics that might be needed <strong>and</strong> a list<br />

of materials that could be used in seeking a solution.<br />

A particular focus for the page or set of three pages<br />

of problems then exp<strong>and</strong>s on these aspects. Each<br />

book is organised so that when a problem requires<br />

complicated strategic thinking, two or three problems<br />

occur on one page (supported by a teacher page with<br />

detailed discussion) to encourage students to find<br />

a solution together with a range of means that can<br />

be followed. More often, problems are grouped as a<br />

series of three interrelated pages where the level of<br />

complexity gradually increases, while the associated<br />

teacher page examines one or two of the problems in<br />

depth <strong>and</strong> highlights how the other problems might be<br />

solved in a similar manner.<br />

R.I.C. Publications ® www.ricpublications.com.au <strong>Problem</strong>-<strong>solving</strong> in mathematics<br />

iii


FOREWORD<br />

Each teacher page concludes with two further aspects<br />

critical to successful teaching of problem-<strong>solving</strong>. A<br />

section on likely difficulties points to reasoning <strong>and</strong><br />

content inadequacies that experience has shown may<br />

well impede students’ success. In this way, teachers<br />

can be on the look out for difficulties <strong>and</strong> be prepared<br />

to guide students past these potential pitfalls. The<br />

final section suggests extensions to the problems to<br />

enable teachers to provide several related experiences<br />

with problems of these kinds in order to build a rich<br />

array of experiences with particular solution methods;<br />

for example, the numbers, shapes or measurements<br />

in the original problems might change but leave the<br />

means to a solution essentially the same, or the<br />

context may change while the numbers, shapes or<br />

measurements remain the same. Then numbers,<br />

shapes or measurements <strong>and</strong> the context could be<br />

changed to see how the students h<strong>and</strong>le situations<br />

that appear different but are essentially the same<br />

as those already met <strong>and</strong> solved. Other suggestions<br />

ask students to make <strong>and</strong> pose their own problems,<br />

investigate <strong>and</strong> present background to the problems<br />

or topics to the class, or consider solutions at a more<br />

general level (possibly involving verbal descriptions<br />

<strong>and</strong> eventually pictorial or symbolic arguments).<br />

In this way, not only are students’ ways of thinking<br />

extended but the problems written on one page are<br />

used to produce several more problems that utilise<br />

the same approach.<br />

Mathematics <strong>and</strong> language<br />

The difficulty of the mathematics gradually increases<br />

over the series, largely in line with what is taught<br />

at the various year levels, although problem-<strong>solving</strong><br />

both challenges at the point of the mathematics<br />

that is being learned as well as provides insights<br />

<strong>and</strong> motivation for what might be learned next. For<br />

example, the computation required gradually builds<br />

from additive thinking, using addition <strong>and</strong> subtraction<br />

separately <strong>and</strong> together, to multiplicative thinking,<br />

where multiplication <strong>and</strong> division are connected<br />

conceptions. More complex interactions of these<br />

operations build up over the series as the operations<br />

are used to both come to terms with problems’<br />

meanings <strong>and</strong> to achieve solutions. Similarly, twodimensional<br />

geometry is used at first but extended<br />

to more complex uses over the range of problems,<br />

then joined by interaction with three-dimensional<br />

ideas. Measurement, including chance <strong>and</strong> data, also<br />

extends over the series from length to perimeter, <strong>and</strong><br />

from area to surface area <strong>and</strong> volume, drawing on<br />

the relationships among these concepts to organise<br />

solutions as well as giving an underst<strong>and</strong>ing of the<br />

metric system. Time concepts range from interpreting<br />

timetables using 12-hour <strong>and</strong> 24-hour clocks while<br />

investigations related to mass rely on both the concept<br />

itself <strong>and</strong> practical measurements.<br />

The language in which the problems are expressed is<br />

relatively straightforward, although this too increases<br />

in complexity <strong>and</strong> length of expression across the books<br />

in terms of both the context in which the problems<br />

are set <strong>and</strong> the mathematical content that is required.<br />

It will always be a challenge for some students<br />

to ‘unpack’ the meaning from a worded problem,<br />

particularly as problems’ context, information <strong>and</strong><br />

meanings exp<strong>and</strong>. This ability is fundamental to the<br />

nature of mathematical problem-<strong>solving</strong> <strong>and</strong> needs to<br />

be built up with time <strong>and</strong> experiences rather than be<br />

iv<br />

<strong>Problem</strong>-<strong>solving</strong> in mathematics www.ricpublications.com.au R.I.C. Publications ®


FOREWORD<br />

diminished or left out of the problems’ situations. One<br />

reason for the suggestion that students work in groups<br />

is to allow them to share <strong>and</strong> assist each other with<br />

the tasks of discerning meanings <strong>and</strong> ways to tackle<br />

the ideas in complex problems through discussion,<br />

rather than simply leaping into the first ideas that<br />

come to mind (leaving the full extent of the problem<br />

unrealised).<br />

An approach to <strong>solving</strong> problems<br />

Try<br />

an approach<br />

Explore<br />

means to a solution<br />

Analyse<br />

the problem<br />

The careful, gradual development of an ability to<br />

analyse problems for meaning, organising information<br />

to make it meaningful <strong>and</strong> to make the connections<br />

among them more meaningful in order to suggest<br />

a way forward to a solution is fundamental to the<br />

approach taken with this series, from the first book<br />

to the last. At first, materials are used explicitly to<br />

aid these meanings <strong>and</strong> connections; however, in<br />

time they give way to diagrams, tables <strong>and</strong> symbols<br />

as underst<strong>and</strong>ing <strong>and</strong> experience of <strong>solving</strong> complex,<br />

engaging problems increases. As the problem forms<br />

exp<strong>and</strong>, the range of methods to solve problems<br />

is carefully extended, not only to allow students to<br />

successfully solve the many types of problems, but<br />

also to give them a repertoire of solution processes<br />

that they can consider <strong>and</strong> draw on when new<br />

situations are encountered. In turn, this allows them<br />

to explore one or other of these approaches to see<br />

whether each might furnish a likely result. In this way,<br />

when they try a particular method to solve a new<br />

problem, experience <strong>and</strong> analysis of the particular<br />

situation assists them to develop a full solution.<br />

Not only is this model for the problem-<strong>solving</strong> process<br />

helpful in <strong>solving</strong> problems, it also provides a basis for<br />

students to discuss their progress <strong>and</strong> solutions <strong>and</strong><br />

determine whether or not they have fully answered<br />

a question. At the same time, it guides teacher<br />

questions of students <strong>and</strong> provides a means of seeing<br />

underlying mathematical difficulties <strong>and</strong> ways in<br />

which problems can be adapted to suit particular<br />

needs <strong>and</strong> extensions. Above all, it provides a common<br />

framework for discussions between a teacher <strong>and</strong><br />

group or whole class to focus on the problem-<strong>solving</strong><br />

process rather than simply on the solution of particular<br />

problems. Indeed, as Alan Schoenfeld, in Steen L (Ed)<br />

Mathematics <strong>and</strong> democracy (2001), states so well, in<br />

problem-<strong>solving</strong>:<br />

getting the answer is only the beginning rather than<br />

the end … an ability to communicate thinking is<br />

equally important.<br />

We wish all teachers <strong>and</strong> students who use these<br />

books success in fostering engagement with problem<strong>solving</strong><br />

<strong>and</strong> building a greater capacity to come to<br />

terms with <strong>and</strong> solve mathematical problems at all<br />

levels.<br />

George Booker <strong>and</strong> Denise Bond<br />

R.I.C. Publications ® www.ricpublications.com.au <strong>Problem</strong>-<strong>solving</strong> in mathematics<br />

v


CONTENTS<br />

Foreword .................................................................. iii – v<br />

Contents .......................................................................... vi<br />

Introduction ........................................................... vii – xix<br />

A note on calculator use ................................................ xx<br />

Teacher notes.................................................................... 2<br />

Stacking shapes................................................................ 3<br />

Painted cubes.................................................................... 4<br />

Cube painting.................................................................... 5<br />

Teacher notes.................................................................... 6<br />

How many digits?............................................................. 7<br />

Teacher notes.................................................................... 8<br />

Star gaze........................................................................... 9<br />

Magic squares/Famous magic squares.......................... 10<br />

Sudoku............................................................................ 11<br />

Teacher notes.................................................................. 12<br />

The water park................................................................ 13<br />

Lily pads <strong>and</strong> frogs.......................................................... 14<br />

Gone fishing.................................................................... 15<br />

Teacher notes.................................................................. 16<br />

Chicken takeaway........................................................... 17<br />

Teacher notes.................................................................. 18<br />

The big race.................................................................... 19<br />

Serial numbers............................................................... 20<br />

Puzzle scrolls................................................................... 21<br />

Teacher notes.................................................................. 22<br />

Samantha’s flower shop.................................................. 23<br />

Herb market.................................................................... 24<br />

At the bakery................................................................... 25<br />

Teacher notes.................................................................. 26<br />

<strong>Number</strong>s in columns....................................................... 27<br />

Teacher notes.................................................................. 28<br />

Calculator problems........................................................ 29<br />

Ice-cream cones.............................................................. 30<br />

Chocolate frogs............................................................... 31<br />

Teacher notes.................................................................. 32<br />

How many?..................................................................... 33<br />

How far?.......................................................................... 34<br />

How much?..................................................................... 35<br />

Teacher notes.................................................................. 36<br />

Tropical Cairns................................................................. 37<br />

Teacher notes ................................................................. 38<br />

Squares <strong>and</strong> perimeters.................................................. 39<br />

More perimeters............................................................. 40<br />

Perimeters in squares.................................................... 41<br />

Teacher notes.................................................................. 42<br />

Beading........................................................................... 43<br />

Library............................................................................. 44<br />

At the station.................................................................. 45<br />

Teacher notes.................................................................. 46<br />

Bookworms..................................................................... 47<br />

Teacher notes ................................................................. 48<br />

Farm trails ...................................................................... 49<br />

Balancing........................................................................ 50<br />

Squares <strong>and</strong> area............................................................ 51<br />

Teacher notes.................................................................. 52<br />

DVD rentals..................................................................... 53<br />

Drive time........................................................................ 54<br />

Clock watching................................................................ 55<br />

Teacher notes.................................................................. 56<br />

On the farm..................................................................... 57<br />

In the barn....................................................................... 58<br />

Market day...................................................................... 59<br />

Teacher notes.................................................................. 60<br />

Shopping......................................................................... 61<br />

Solutions ..................................................................62–66<br />

Isometric resource page .............................................. 67<br />

0–99 board resource page ............................................ 68<br />

4-digit number exp<strong>and</strong>er resource page (x 3) ............... 69<br />

10 mm x 10 mm grid resource page ............................. 70<br />

15 mm x 15 mm grid resource page ............................. 71<br />

Triangular grid resource page ...................................... 72<br />

vi<br />

<strong>Problem</strong>-<strong>solving</strong> in mathematics www.ricpublications.com.au R.I.C. Publications ®


TEACHER NOTES<br />

<strong>Problem</strong>-<strong>solving</strong> objective<br />

To analyse <strong>and</strong> use information in word problems.<br />

Materials<br />

place value chart or a calculator<br />

Focus<br />

These pages explore word problems that mostly require<br />

addition or subtraction. Students need to determine what<br />

the problem is asking <strong>and</strong>, in many cases, calculate more<br />

than one step in order to find solutions. Analysis of the<br />

problems reveals that some questions contain additional<br />

information that is not needed.<br />

If necessary, materials can be used to assist with the<br />

calculation as these problems are about reading for<br />

information <strong>and</strong> determining what the problem is asking<br />

rather than computation or basic facts.<br />

Discussion<br />

Page 13<br />

These problems involve more than one step <strong>and</strong> may<br />

involve addition as well as subtraction. The wording<br />

has been kept simple to assist with the problem-<strong>solving</strong><br />

process.<br />

Students may choose a number of different ways to find<br />

a solution. For example, the second problem about people<br />

getting out (43) could be subtracted from the people going<br />

swimming (79) <strong>and</strong> then this number (36) could be added<br />

to 397 or, alternatively, 79 could be added to 397 <strong>and</strong> then<br />

43 subtracted to obtain a solution. Students should be<br />

encouraged to explore <strong>and</strong> try different ways of arriving<br />

at a solution.<br />

Page 15<br />

A careful reading of each problem is needed to determine<br />

what the question is asking. In some cases, there is more<br />

information than needed <strong>and</strong> some problems contain<br />

numbers that are not needed to find a solution. Most<br />

problems require more than one step <strong>and</strong> both addition<br />

<strong>and</strong> subtraction are needed at times.<br />

Again, there are a number of ways to find a solution<br />

<strong>and</strong> students should be encouraged to explore <strong>and</strong> try<br />

different possibilities of arriving at an answer. The last<br />

question involves students underst<strong>and</strong>ing that perch <strong>and</strong><br />

carp are varieties of fish, while yabbies are crustaceans.<br />

Possible difficulties<br />

• Inability to identify the need to add, subtract or<br />

multiply<br />

• Confusion over the need to carry out more than one<br />

step to arrive at a solution<br />

• Using all the numbers listed in the problems rather<br />

than just the numbers needed<br />

Extension<br />

• Explore the possibilities as to whether the dry season<br />

would be before or after spring.<br />

• Discuss how some problems can have more than one<br />

answer depending on different interpretations.<br />

• Students could write their own problems <strong>and</strong> give<br />

them to others to solve.<br />

Page 14<br />

This investigation relates to information about a lake with<br />

lily pads <strong>and</strong> frogs. The scenario begins with a certain<br />

number of frogs <strong>and</strong> lily pads. As new information is<br />

introduced, the numbers change to meet the new criteria;<br />

lily pads flower, grow <strong>and</strong> die while the frogs move from<br />

one lake to another.<br />

Students are required to keep track of the new information<br />

<strong>and</strong> use it to answer the subsequent questions. The<br />

last question has two possible answers as it depends<br />

on whether spring is before or after the dry season.<br />

Students should be encouraged to explore the different<br />

possibilities.<br />

12<br />

<strong>Problem</strong>-<strong>solving</strong> in mathematics www.ricpublications.com.au R.I.C. Publications ®


THE WATER PARK<br />

1. 361 adults <strong>and</strong> 173 children go<br />

through the gates before lunch,<br />

<strong>and</strong> 219 adults <strong>and</strong> 106 children<br />

enter after lunch. How many<br />

more adults than children are<br />

there?<br />

2. A total of 397 people are<br />

swimming in the six pools.<br />

Another 79 people go swimming<br />

while 43 people get out. How<br />

many people are now swimming<br />

in the pools?<br />

3. 248 people are lying on their<br />

towels. Later, 78 people go<br />

swimming, 26 people go for a<br />

walk <strong>and</strong> 36 people leave <strong>and</strong><br />

get something to eat. How many<br />

people are still lying on their<br />

towels?<br />

4. In the water, 93 people are floating<br />

on swimming mats, 134 are<br />

swimming <strong>and</strong> 83 are wading in<br />

the shallow water. Soon, another<br />

21 people with swimming mats<br />

arrive, but 14 also get out. How<br />

many people are now floating on<br />

swimming mats?<br />

5. At the cafeteria, 143 people are<br />

sitting eating lunch <strong>and</strong> 31 are<br />

st<strong>and</strong>ing in line waiting to order<br />

lunch. Two large tables of 12 finish<br />

their lunch <strong>and</strong> leave. How many<br />

people are now in the cafeteria?<br />

6. In the wave pool, 73 surfers are<br />

waiting to catch a wave. A large<br />

wave comes <strong>and</strong> 36 surfers catch<br />

<strong>and</strong> ride it to the beach. How<br />

many did not catch the wave?<br />

R.I.C. Publications ® www.ricpublications.com.au <strong>Problem</strong>-<strong>solving</strong> in mathematics<br />

13


LILY PADS AND FROGS<br />

A lake has 279 lily pads <strong>and</strong> 372 frogs.<br />

1. 87 of the lily pads are in flower. If each lily pad has three flowers, how<br />

many flowers are there altogether?<br />

2. How many lily pads are not in flower?<br />

3. Frogs like to sleep under the lily flowers. How many frogs can not sleep<br />

under a flower?<br />

4. When the rains come, 38 more lily pads burst into flower. How many lily<br />

pads are now in flower?<br />

5. Are there now enough lily flowers for each frog to sleep under?<br />

6. During spring, 129 new lily pads grow, 186 tadpoles turn into frogs <strong>and</strong><br />

75 lily pads die. How many lily pads are now in the lake?<br />

7. During the dry season, some frogs move to another lake. If 148 frogs<br />

move to another lake, how many stay behind?<br />

14<br />

<strong>Problem</strong>-<strong>solving</strong> in mathematics www.ricpublications.com.au R.I.C. Publications ®


GONE FISHING<br />

1. On Saturday, 97 large yabbies, 21 small yabbies <strong>and</strong> 57 carp were<br />

caught. On Sunday, 126 large yabbies, 34 small yabbies <strong>and</strong> 83 carp<br />

were caught. How many yabbies were caught?<br />

2. During the week, 163 perch, 394 carp <strong>and</strong> 304 bass were caught in the<br />

dam. How much more bass than perch was caught?<br />

3. During a fishing competition, 923 perch were caught, tagged <strong>and</strong> then<br />

released back into the dam. 359 tagged perch were caught in October,<br />

271 in November <strong>and</strong> 106 in December. How many tagged perch have<br />

not been caught?<br />

During the first weekend in June, 239 perch, 56 large yabbies, 17 small<br />

yabbies <strong>and</strong> 43 carp were caught. The next weekend, 161 perch, 79 large<br />

yabbies, 24 small yabbies <strong>and</strong> 65 carp were caught.<br />

4. During which weekend were the most yabbies caught?<br />

5. During which weekend were the least amount of fish <strong>and</strong> yabbies<br />

caught?<br />

6. During which weekend were the most fish caught?<br />

R.I.C. Publications ® www.ricpublications.com.au <strong>Problem</strong>-<strong>solving</strong> in mathematics<br />

15


SOLUTIONS<br />

Note: Many solutions are written statements rather than just numbers. This is to encourage teachers <strong>and</strong> students to solve<br />

problems in this way.<br />

THE WATER PARK..............................................Page 13<br />

1. 301 more adults<br />

2. 433 people swimming in the pools<br />

3. 108 people lying on their towels<br />

4. 100 people floating on swimming mats<br />

5. 150 people<br />

6. 37 surfers did not catch a wave.<br />

LILY PADS AND FROGS ....................................Page 14<br />

1. 261 flowers<br />

2. 192 lily pads<br />

3. 111 frogs<br />

4. 125 lily pads are in flower<br />

5. Yes, there are 375 flowers<br />

6. 333 lily pads<br />

7. If the dry season is before spring, 224 frogs stayed<br />

behind. If the dry season is after spring, 410 frogs stayed<br />

behind.<br />

GONE FISHING ..................................................Page 15<br />

1. 278 yabbies were caught.<br />

2. 141 more bass were caught.<br />

3. 187 perch have not been caught.<br />

4. Second weekend<br />

5. First weekend<br />

6. First weekend: 282 fish were caught—yabbies are not<br />

fish.<br />

R.I.C. Publications ® www.ricpublications.com.au <strong>Problem</strong>-<strong>solving</strong> in mathematics<br />

63

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